The newest edition of the SETI radio show "Are We Alone" is up, and in the segment called Skeptic Check astronomer Seth Shostak and I poke fun at the latest silliness about Betelgeuse and the Mayan doomsday. The rest of the show is, as usual, really good and fun to listen to (all about ESP — but you knew that already), so head over there and give it a download. But do it before December 21, 2012.

Comments (26)

Awesome red supergiant
Swollen surface so huge
Six hundred odd light years off
Are you still there?
We won’t know till
So many years have passed
Yet certainly you’ll have someday
One almighty goshdurn blast! 😉

What’s with this obsession with Dec 21, 2012? That’s not the end of the world. It’s the beginning of the new one. The new long count begins on Dec 21, 2012. Which means …

OMG, the world is ending 12/20/2012 or 2012/12/20. There’s even less time than I thought.

All of you doomsayers need to get your dates right. A lot of procrastinators will be extremely pissed when the world ends a day early.

The Mayans were amazing astronomers to be able to predict when the blast from a supernova 640 ly away would reach and destroy the Earth. It’s a shame they couldn’t predict the fall of their own civilization and save it.

So tired of 2012 and the doomsayers. Tired of debunking it at school with my students. Excellent podcast and your spot on Betel was excellent save one matter. Betelgeuse could explode tonight, or tomorrow, or eventually without making the point that when we do see the light it will have actually explodes roughly 640 years ago (I believe Betelgeuse is around 640 ly from us). When such a wonderful event happens, the public will think they are seeing this in real time. We know they aren’t but shouldn’t we at least attempt to educate them properly or is it too complicated for the public to understand?

Earth actually ended on Oct 4, 1990 but we didn’t notice, because it was Childhoods End, so we just recreated everything the way it was. We didn’t bother telling everyone because we didn’t want to disturb the “stupid people”.

Make enough doomsday predictions and eventually it will happen but then there won’t be anyone to brag to about being right so, Why Worry?

Not necessarily thicker atmosphere, if the planet radius is larger than Earth.

Well either it has a lot more mass, which means more volcanism which means more volatiles in the atmosphere and also a deeper gravity well to keep it that way.

Or it means a lot smaller density. But then it consist mostly of lighter elements, which means a lot more volatiles.

And higher insolation… It’s just 7K warmer! Let’s say 13º .

It is not just that. it is that plus a much higher greenhouse effect, all the way until you get atmosphere saturated with water vapor, and a hundreds of degrees hot “ocean” of supercritical fluid below it.

Regarding KOI-701.03, that increase in effective temperature is not necessarily fatal for habitability prospects, though it does put it closer to the inner boundary of the HZ. Selsis et al. (2007) in their study of habitability determined an upper limit of about 270 K for the blackbody temperature of a habitable planet. (Being below this limit does not necessarily guarantee habitability, e.g. the blackbody temperature of Venus is about 230 K thanks to the global layer of highly reflective acid clouds)

What is more worrying is the 1.73 Earth radii which probably implies substantial amounts of ice/gas. Note that all confirmed “super-Earths” apart from the very hottest ones (CoRoT-7b, Kepler-10b) are actually “mini-Neptunes”. If KOI-701.03 follows this pattern it probably means it has a thick, hydrogen-rich atmosphere that would screw up the habitability prospects no end.

I think when all we’ve got is a radius and orbital distance it’s a wee bit premature to speculate too firmly on things like atmospheric composition and habitability.

One of the cheap shots I hate at most, is telling the other side that we have not enough information and that he is thus drawing premature conclusions.
Without saying anything specific about where and why the other sides arguments validity is uncertain.

Because we never have the complete information, one can (ab)use it ad infinitum. Just wait till all data are in,, we don’t know enough yet, who we are to event think that we can solve this one, etc.
One can that use that canard ad nauseam, because, no matter how much information we gather, there is still a greater amount of information we don’t have yet.
If you don’t give any specifics about what relevant information we are missing, you can easily bulldoze away even things that really follow from the data we already have.
For example, the +7k blackbody temperature would most probably kill earth too. ( earth climate sensitivity is cca 3K per 1K of driving, so 7k would translate into 36degC average temperature, more than enough to start runaway accumulation of water vapor in the atmosphere ) And something with a bigger diameter than earth we really can not expect to have a thinner atmosphere than earth.

In many ways working with these effective temperatures is extremely misleading as they depend critically on the planetary albedo and the amount of redistribution around the planet, both of which are unknown quantities. Earth’s blackbody temperature is higher than that of Venus thanks to the reflective atmosphere of Venus more than compensating for the planet being closer to the Sun.

Better to work with incident flux instead, as that involves far fewer unknown quantities. Going back to the numbers in the original paper, the value for KOI-701.03 is 13% greater than the incident flux for Earth, assuming the orbit is circular (eccentric orbits receive a boost of 1/sqrt(1-e^2) where e is the eccentricity). This corresponds to an equivalent location of about 0.94 AU in our solar system, which is pretty close to widely-quoted estimates of the inner HZ boundary of around 0.95 AU.

Now KOI-701 has a lower effective temperature than the Sun (4869 K vs 5780 K), which also will change things – in particular it will decrease the albedo of the planet thanks to less efficient Rayleigh scattering in the atmosphere. This shifts the HZ outwards. Going by the parametrisations of various HZ limits given in Underwood, Jones and Sleep (2003), the three HZ inner boundaries would be at fluxes of 1.67 (recent Venus), 1.22% (runaway greenhouse), 1.04 (water loss) relative to Earth. So KOI-701.03 would not yet be at runaway greenhouse conditions, but there would be significant quantities of water vapour in the upper atmosphere which would gradually be lost via photodissociation into hydrogen and oxygen. Depending on the initial water inventory of the planet and the rate of escape of hydrogen, this may or may not be a problem.

Of course, this all assumes a terrestrial-type planet, if the planet is a mini-Neptune the story is going to be very different.

Having gone over the data it is fairly simple to create a spreadsheet which determines whether a given Kepler candidate is in the HZ as defined by the Underwood, Jones and Sleep (2003) paper. Doing that reveals that 24 candidates are in the HZ if the widest possible definition is used. Compare this to the 54 that the Kepler team announced: most of the “habitable zone” candidates are too close to the star.

Going with the most conservative HZ definition, eight candidates match the criteria. Of these eight, most are Neptune-sized. The smallest is KOI-1026.01, which at 1.8 Earth radii is probably a mini-Neptune. For those looking for habitable moons there is one Jupiter-scale candidate in the conservative HZ, the 13.4 Earth radius KOI-433.02 which is located in a candidate multi-planet system.

frankenstein monster, before one goes about declaring something “Venus-kind”, of “mini-Neptune” at the very least one should have a density measurement. I’m not asking for much – this data should be readily available very soon.

It should also be possible in the not too distant future to obtain some direct measurements from which to infer atmospheric composition, since these are transiting planets.

I explained already, why both low and high density won’t help to make the planet more habitable. So, what is the point.

No you did not. If you tried, you did it very poorly.

Are you referring to here?

Well either it has a lot more mass, which means more volcanism which means more volatiles in the atmosphere and also a deeper gravity well to keep it that way.

This is no explanation. Just a statement by fiat of what you believe.

What is your justification that the relationship between mass, volcanism and atmospheric thickness is so regular and certain that you can make such a claim knowing only planetary diameter? With only the evidence of earth and Venus, and no examples of planets in the size range between earth and Neptune to back up this conjecture?

With no reference to age of star system (affecting time for atmospheric stripping and cooling of volcanism), volatility of parent star (affecting rate of atmospheric stripping), formation history of the planets, possibility of orbital migration, large impact history and the possibility of an impact blowing away most of the primordial atmosphere (as has been hypothesized to have happened to earth but not with Venus, accounting for the differences in atmospheres between the two), among just a few potential variables.

Because we never have the complete information, one can (ab)use it ad infinitum.

As far as I am concerned, in this area, we don’t merely have incomplete information. We have no information. For planets 1-2 earth diameters, with only an N of 1, nothing, absolutely nothing we currently have derived from studying that N (earth), has any context, and therefore cannot validly be used to make predictions concerning other planets. We have no idea which things are unique to earth, and which are not. Which matter and which do not, which are specific and which are universal. Not until we get at least one more direct measurement of one exoplanetary atmosphere, in that size range.

You can make suppositions based on incomplete information, but you cannot with no information.